The science that unlocked a rare genetic mutation in the Folbiggs, and set Kathleen free

The gene mutation that triggered the inquiry is so rare, there are only 135 known cases in the world. Three of those were in the Folbigg family. Analysis of the children's DNA found Kathleen Folbigg had passed the mutation on to her two daughters. The inquiry also heard evidence that one of the boys had a different genetic disorder that likely led to his death.